.. alls, but a chamber of equal dimension with the aisle. This arrangement not only affords additional spaces but also, by reason of the greater height of the edifice, might seem to facilitate the provision of a more liberal supply of light, unimpeded by neighbouring buildings. This last mentioned advantage is, however, almost entirely negatived by the circumstance that, in this class of buildings, each bay of the gallery is subdivided by means of coupled or grouped arches, so that the additional obstruction offered to the passage of the light almost entirely counterbalance the possible gain through additional fenestration. We say the possible gain because, in fact, the galleries of these churches are but sparingly provided with windows. In these churches (which to the English reader should be of special interest by reason of their affinity in point of construction to the Westminster cathedral) the aisle is usually cross-vaulted, while the gallery has a quadrant vault abutting in the wall of the nave just below the springing of the transverse arches.
The most noteworthy examples are found at Clermont-Ferrand (Notre Dame du Port), Issoire (St-Paul), and Conques. To the same family belongs moreover, the great church of St-Sernin at Toulouse already mentioned, which is distinguished from those previously named by having a double aisle. At Nevers the church of St-Etienne resembles those at Clermont, Issoire, and Conques, except that it is provided with a range of upper windows which break through the barrel-vaulting, somewhat after the fashion which afterwards became so common in Italy in churches of the Renaissance period. The inherent shortcomings of the barrel-vault, especially when used as a roof for the nave of an aisled church, have been sufficiently illustrated. These disadvantages, so far as structural stability and fenestration are concerned, might indeed be overcome by adopting the system of a succession of transverse barrel-vaults, such as are seen in the unique instance of the church of St-Philibert at Tournus.
Such a construction is, however, ponderous and inelegant, and never came into general use (Moore, Gothic Architecture, 42). The system of cross-vaulting, which has now to be considered, may be regarded as a combination of longitudinal with transverse barrel-vaulting, inasmuch as it may be described as consisting of a central barrel which is penetrated or intersected by a series of transverse vaults, corresponding of course to the successive bays or compartments of the nave. The advantages of cross-vaulting are threefold. In the first place the total amount of the outward lateral thrust is very greatly diminished, since one half of it is now replaced by longitudinal thrusts, which, being opposed in pairs, neutralize one another. Secondly, all that is left of the lateral thrust, as well as the longitudinal thrusts, and the whole of the vertical pressure instead of being distributed throughout the whole length of the building, is now collected and delivered at definite points, namely the summits of the columns or pillars. Thirdly and lastly, a perfectly developed system of cross-vaulting makes it possible so to heighten the clerestory windows that their archivolts shall reach the utmost interior height of the building, and so to broaden them that their width between reveals may approximate very closely to the interval between column and column below.
By these improvements (as ultimately realized in the perfected Gothic of the thirteenth century) the somewhat rudimentary design of the ancient Roman basilica may be said to have reached the highest development of which it is capable. The gradual development of cross-vaulting it is to be observed, did not take place in those districts of Southern and Central France which had already become the home of the barrel-vault and to a less degree of the cupola, but first in Lombardy then in Germany, and finally in Northern France and in England. In these countries the evolution of the Romanesque timber-roofed basilican church had — with local variations of course — reached a far more advanced stage than was ever attained in these regions in which the adoption of barrel-vaulting at a relatively early date had in a manner put a check on architectural progress. And it is noteworthy that in Lombardy and Germany, when cross-vaulting was first adopted, its development was far less complete than in Northern France, and that in like manner the advance towards perfection was both less rapid and less complete in Normandy than in Picardy and the Ile-de-France. These two districts were the last to adopt the system, but it was here that it was within the brief space of less than fifty years (1170-1220), brought to its final perfection. The reason may probably have been, as Dehio and von Bezold suggest, that the architects of the Ile- de-France, in the days of Philip Augustus and St. Louis, were less trammelled than those of Normandy by the traditions of a school.
The comparative lack of important architectural monuments of an earlier date left them, say these writers, a more open field for their inventive enterprise (op. cit. I, 418). The simplest form of cross-vaulting is of course that which is formed by the intersection of two cylindrical barrel-vaults of equal span. And this, without the use of ribbed groining, was the method mostly adopted by the Roman builders in their civic edifices. In the case of a pillared or columned church, however, this method had its disadvantages.
In particular, having regard to the dimensions of the aisle and its vaulting, the builders of Northern Europe had all but universally adopted the plan of so spacing the columns and pillars which flank the nave that the intervals between them should be one-half the width of the church. Now the only means by which an equal height could be given to vaults of unequal span was the use of the pointed arch; and so it came about that the pointed arch was adopted, not primarily for aesthetic reasons, but rather for constructive purposes. And the same is to be said of the use of ribbed groining. The medieval builders, who, as has been said above, possessed neither a tenacious mortar nor the command of an abundant supply of rough labour, and who therefore could not — even had they wished it — have adopted the massive concrete masonry of the Romans, were driven by the very necessities of the case to aim at the same time to depend for stability not on the cohesion of the materials, but on the reduction of thrusts to a minimum, and on their skilful transmission to points where they could be effectively resisted. It was, then, plainly desirable to substitute for a vaulting of uniform thickness a framework of ribs on which a comparatively thin layer of stones (cut to the requisite curvature) could be laid, and as far as possible to lighten the whole construction by moulding the ribs and likewise the columns which supported the vaulting.
The same principle of aiming at lightness of construction led to the elimination, as far as possible, of arches of the nave. This was done by the enlargement of the windows and the development of the triforium, till the entire building, with the exception of the buttresses, and of the spandrels below the triforium, became a graceful framework of grouped shafts and interlacing ribs (Moore, op. cit., 17). The final stage in the evolution of architecture of the pointed arch was not, however, reached, until, for the solid Romanesque buttresses, which rested on the vaulting of the aisles, and which were not only clumsy but often proved inadequate for their purpose, the genius of the Gothic builders hit upon the epoch-making device of the flying buttress. By means of this device the thrust of the main vaulting was not, indeed, as has been too often said, met by a counter-thrust, but was transmitted to the solid buttresses, mostly weighted with pinnacles, which were now built outwards to a great distance from the aisles, and the spaces between which were sometimes utilized, and might with advantage have been more often utilized, for a range of lateral chapels. The subject of Gothic architecture in its details is, however, one that needs separate treatment, and for present purposes this very inadequate indication of some of the general principles involved in its development must suffice.
THE CIRCULAR CHURCH AND ITS DERIVATIVES It was stated at the outset of the article that all ecclesiastical architecture may be said to have been devel- oped from two primitive germs, the oblong and the circular chamber. Of those very numerous churches, principally, but by no means exclusively, Eastern or Italian, which may be regarded as the products of the second line of development, we shall speak very briefly. That a circular chamber without any kind of annex was unsuitable for the ordinary purposes of public worship is plain enough. And the most obvious modification of this rudimentary form was to throw out a projecting sanctuary on one side of the building, as in St. George’s, Thessalonica, or in the little church of S.
Tommaso in Limine, near Bergamo. It was hardly less obviously convenient to build a projecting porch or narthex on the opposite side, as in St. Elias’s, also at Thessalonica, and to complete the cross by means of lateral projection, as in the sepulchral chapel of Galla Placidia at Ravenna. Thus it was that churches having the form of a Greek cross, as well as other varieties of what German authors call the Centralbau, may be said to owe their origin to a very simple process of evolution from the circular domed building. Among the almost endless varieties on the main theme may be here enumerated: buildings in which a circular, or polygonal, or quadrilateral aisle, whether in one or more stories, surrounds the central space, buildings in which, though the principal open space is cruciform, and the whole is dominated by a central cupola, the ground- plan shows a rectangular outline, the cross being, as it were, boxed within a square; and buildings in which one of the arms of the cross is considerably elongated, as in the Duomo at Florence, St.
Peter’s in Rome, and St. Paul’s in London. The last-named modification, it is to be observed, has the effect of assimilating the ground-plan of those great churches, and of many lesser examples of the same character, to that of the Romanesque and Gothic cruciform buildings whose genealogical descent from the columned rectangular basilica is contestable. Among ecclesiastical edifices of historical importance or interest which are either circular or polygonal, or in which the circular or polygonal centre predominates over subsidiary parts of the structure, may be mentioned the Pantheon in Rome, St. Sergius at Constantinople, S. Vitale at Ravenna, S. Lorenzo at Milan, the great baptisteries of Florence, Siena, and Pisa, and the churches of the Knights Templars in various parts of Europe.
St. Luke at Stiris in Phocis, besides being an excellent typical instance of true Byzantine architecture, affords a good example of the boxing of a cruciform building of the Greek type, by enclosing within the walls the square space between the adjacent limbs of the cross. Practically, however, the full development of cruciform from circular buildings became possible only when the problem had been solved of roofing a square chamber with a circular dome. This has in some cases been done by first reducing the square to an octagon, by means of squinches or trompettes, and then raising the dome on the octagon, by filling in the obtuse angles of the figure with rudimentary pendentives or faced corbelling. But already in the sixth century the architect and builder of Santa Sophia had showed for all time that it was possible by means of true pendentives, to support a dome, even of immense size, on four arches (with their piers) forming a square. The use of pendentives being once understood, it became possible, not only to combine the advantages of a great central dome with those of a cruciform church, but also to substitute domical for barrel- vaulting over the limbs of the cross, as at S.
Marco, Venice, St-Front, Prigueux, and S. Antonio, Padua, or even to employ domical vaulting for a nave divided into square bays, as in the cathedral at Angouleme and other eleventh century churches in Perigord, in S. Salvatore at Venice, in the London Oratory, and (with the difference that saucer domes are here employed) in the Westminster Cathedral. Nor should it be forgotten that in the nave of St. Paul’s, London, the architect had shown that domical vaulting is possible even when the bays of nave or aisles are not square, but pronouncedly oblong. Indeed, if account be taken of the manifold disadvantages of barrel-vaulting as a means of roofing the nave of a large church, it may safely be said that the employment of some form of the dome or cupola is as necessary to the logical and structural perfection of the architecture of the round arch as ribbed groining and the use of flying buttresses are necessary to the logical and structural perfection of the architecture of the pointed arch. SYSTEMS AND STYLES OF ARCHITECTURE IN RELIGION TO MODERN NEEDS A word must now be said, in conclusion, as to the merits of the several systems and styles of architecture, more especially in relation to the needs of our own day.
Of systems, indeed, there are in truth only three, the trabeate or that of which the horizontal lintel may be regarded as the generating element, and which of necessity postulates a timber roof; that of the round arch, which by virtue of the law of economy postulates, as has been said, the use of domical rather than barrel-vaulting and that of the pointed arch, which, if carried to perfection postulates ribbed groining and the use of the flying buttress. The second system, however, admits of two methods of treatment which are sufficiently distinctive to be classed as two styles, viz. the neoclassical, or Renaissance, and the Byzantine, and which shall be particularized presently. Now the trabeate system, or that of the timber roof, may be very briefly dismissed. In the great majority of cases we must, indeed, of necessity be content with such a covering, for our churches; but no one would choose a wooden roof who could afford a vaulted building.
Again, the various types of Romanesque architecture, with their imperfect and tentative methods of vaulting, though historically of great interest, should be regarded as finally out of court. On the other hands of the Gothic architecture of the thirteenth century as exemplified in the great cathedrals of Northern France and of Cologne, it mas be quite fearlessly asserted: that every single principle of construction employed therein was the outcome of centuries of practical experience, in the form of successive and progressive attempts to solve the problems of church vaulting; that the great loftiness of these buildings was not primarily due (as has been sometimes suggested) to any mere Emporstreben, or upward-soaring propensity, but was simply the aggregate result of giving to the windows of the aisles and of the clerestory a height in suitable proportion to their width, and to the triforium a height sufficient to allow of the abutment of the aisle roof; and that every subsequent attempt to modify in any substantial particular, this perfected Gothic style, was of its nature retrogressive and decadent, as may be illustrated from the English perpendicular and the Italian and Spanish varieties of Gothic architecture. Nevertheless it must be admitted that thirteenth-century Gothic, though perfect of its kind, has its limitations, the most serious of which — in relation to modern needs — is the necessarily restricted width of the nave. When the architect of the Milan cathedral attempted to improve on his French predecessors by exceeding their maximum width of fifty feet, and to construct a Gothic building with a nave measuring sixty feet across it was found impossible, as the building proceeded, to carry out the original design without incurring the almost certain risk of a collapse, and hence it was necessary to depress the clerestory to its present stunted proportions. Now under modern conditions of life, especially in the case of a cathedral of first-class importance, a nave of far greater width is by all means desirable; and in order to secure this greater width it is necessary either to fall back on the unsatisfactory compromise of Italian or Spanish Gothic, as illustrated in the cathedrals of Milan, Florence, or Gerona, or else to adopt the principle of the round arch, combined, by preference, with domical vaulting. This, as everyone knows, is what Mr.
Bentley has done, with altogether conspicuous success, in the case of the Westminster Cathedral. Of the design of this noble edifice it is impossible to speak here. But it may be worth while to indicate one main reason for the choice of the Byzantine rather than the neoclassic or Renaissance treatment of the round-arch system. The principal difference between the two is this: that, whereas the neoclassical style, by its use of pilasters, treats every pier as though it were a cluster of huge, flat-faced columns; the Byzantine boldly distinguishes between piers and columns, and employs the latter exclusively for the purposes which monolithic shafts are suited to fulfil, for instance the support of a gallery while the piers in a Byzantine building make no pretence of being other than what they are, viz., the main supports of the vaulting. The Byzantine method of construction was employed at Westminster has the further advantage that it brings within the building the whole of the spaces between the buttresses thereby at the same time increasing the interior dimensions and avoiding the awkward appearance of ponderous external supports.
Nor is the Byzantine style of architecture suitable for a great cathedral alone; and one may venture to hope that the great experiment which has been tried at Westminster will be fruitful of results in the future development of ecclesiastical architecture.